US President Barack Obama's promises to reform government surveillance drew a tepid reaction overseas, while many in the telecommunications industry said the plans did not go far enough.

After months of revelations that strained US relations with allies and cast a harsh light on the National Security Agency's global surveillance reach, Obama's speech on Friday was aimed at least in part at reassuring the world of his country's intentions.

But the initial reaction overseas suggested he still had a significant way to go to heal the rifts, with many wondering why he didn't offer more specific protections.

In Germany, where revelations that the NSA had been eavesdropping on the calls of Chancellor Angela Merkel stirred deep anger and unusually tough criticism of Washington, Obama's promises to rein in the excesses of US spying were met with a tepid welcome from the government - and scorn from some analysts. Government spokesman Steffen Seibert tweeted that Berlin would appreciate better safeguards of the rights of non-US citizens but would need more time to review Obama's words in detail.

Obama in his speech promised greater privacy protections for foreigners. But the new rules have yet to be written, leaving the possibility that intelligence officials will still have wide discretion in sweeping up information about private citizens overseas.

Obama also said he had ordered new restrictions on spying against allied foreign heads of state. But the president did not define who would be considered an ally, nor did he promise an end to spying against foreign leaders' aides, advisers or opponents.

The seemingly limited nature of the restrictions prompted German blogger and author Sascha Lobo to comment on Twitter: "Good to know that in the future you can escape surveillance by simply becoming chancellor."

Reaction was muted in Britain, which has been shown in leaked documents to be a key partner with the United States in global surveillance efforts.

The government released a statement affirming that a parliamentary committee would review British law to find "the appropriate balance between our individual right to privacy and our collective right to security".

But British Prime Minister David Cameron has not come under the same sort of pressure to speak out on the issue in the way that Obama has. Tony Travers, a professor at the London School of Economics, said that was unlikely to change.

"Britain has always had such a powerful tradition of secrecy," he said. "I doubt there have been anguished telephone calls across the Atlantic to get a change in American intelligence-agency behaviour."

In other regions where the NSA revelations have made a big impact - including Latin America - there was no rush from governments to embrace Obama's vows. Officials in Brazil, where President Dilma Rousseff has been outspoken in condemning the NSA surveillance, said they would have no comment.

Phone companies said they feared the centrepiece reform - changes to how the government collects bulk phone metadata - would simply shift the collection and storage of that information to them.

"This would make us a target. It doesn't end the programme but puts it on us," said a telecoms industry official.

In a statement, the lobbying group CTIA-The Wireless Association stressed that it believed security and privacy could be achieved "without the imposition of data-retention mandates that obligate carriers to keep customer information any longer than necessary for legitimate business purposes".

Technology firms including Microsoft, Google and Facebook said in a joint statement that the commitments outlined by Obama "represent positive progress" but added that "crucial details remain to be addressed".